Transplantation of healthy retinal pigment epithelium (RPE) into the subretinal space may become a useful treatment for patients with various retinal degenerations, including Staargardt's disease, macular degeneration, and some forms of retinitis pigmentosa. Previous workers have introduced RPE cells by passing a needle through the sclera, by tunneling through the anterior chamber over the iris root, or by cell injection into the subretinal space through the pars plana. However, few experiments have been done on the feasibility of performing RPE transplants using the modern pars plana vitrectomy techniques that are likely to be useful in humans. The purpose of this research program is to develop the techniques that will be required for the transplantation of healthy RPE cells onto Bruch's membrane in the human. Our goal is to develop these pars plana vitrectomy techniques by using the domestic pig as our experimental model. Initially, we will perform experiments to examine the effects of surgical debridement of the RPE in the domestic pig. We will then transplant donor RPE cells into the subretinal space using two complimentary techniques. First, we will inject suspensions of dissociated to repopulated Bruch's membrane and form a healthy, uniform monolayer of pigmented RPE. We will compare the ability of freshly harvested RPE and RPE from tissue culture to reattach to Bruch's membrane in these experiments. Second, we will transplant sheets of RPE stabilized in gelatin into the subretinal space, using monolayers of RPE attached to their native Bruch's membrane of RPE monolayers grown on extracellular matrix. Our goal is all of these studies is to replace denuded RPE with a healthy monolayer of RPE on Bruch's membrane.